Radiation Oncology Journal

  • 제28권4호
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  • Pages.238-248
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  • 2010
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  • 2234-1900(pISSN)
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  • 2234-3156(eISSN)
대한방사선종양학회 (The Korean Society for Radiation Oncology)
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폐암환자의 종양추적 정위방사선치료를 위한 삼차원 및 사차원 방사선치료계획의 비교

Comparison of Three- and Four-dimensional Robotic Radiotherapy Treatment Plans for Lung Cancers

  • 채규영 (경상대학교 의과대학 방사선종양학교실) ;
  • 임영경 (경상대학교 의과대학 방사선종양학교실) ;
  • 강기문 (경상대학교 의과대학 방사선종양학교실) ;
  • 정배권 (경상대학교 의과대학 방사선종양학교실) ;
  • 하인봉 (경상대학교 의과대학 방사선종양학교실) ;
  • 박경범 (경상대학교 의과대학 신경외과학교실) ;
  • 정진명 (경상대학교 의과대학 신경외과학교실) ;
  • 김동욱 (경희대학교 동서신의학병원 방사선종양학과)
  • Chai, Gyu-Young (Departments of Radiation Oncology, Gyeongsang National University Hospital) ;
  • Lim, Young-Kyung (Departments of Radiation Oncology, Gyeongsang National University Hospital) ;
  • Kang, Ki-Mun (Departments of Radiation Oncology, Gyeongsang National University Hospital) ;
  • Jeong, Bae-Gwon (Departments of Radiation Oncology, Gyeongsang National University Hospital) ;
  • Ha, In-Bong (Departments of Radiation Oncology, Gyeongsang National University Hospital) ;
  • Park, Kyung-Bum (Departments of Neurosurgery, Gyeongsang National University Hospital) ;
  • Jung, Jin-Myung (Departments of Neurosurgery, Gyeongsang National University Hospital) ;
  • Kim, Dong-Wook (Department of Radiation Oncology, Kyung Hee University International Medical Service)
  • 투고 : 2010.10.27
  • 심사 : 2010.11.22
  • 발행 : 2010.12.31
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초록

목적: 폐암환자의 종양추적 정위방사선치료에서 삼차원 및 사차원치료계획의 선량분포 차이를 비교하였고 선량계산 알고리즘에 따른 폐의 비균질성 보정 결과에 커다란 차이가 있음을 확인하고자 하였다. 대상 및 방법: 7명의 폐암환자를 대상으로 전향적 호흡동조된 사차원 컴퓨터단층촬영 영상을 얻었다. 획득한 영상은 환자의 호흡에 대응하는 10개의 삼차원단층촬영 영상이며 이를 바탕으로 사차원치료계획이 수립되었다. 사차원 치료계획에서는 종양과 주변장기의 움직임을 고려하여 X선의 방향과 선량분포를 최적화한다. 사차원치료계획에서 최적화된 빔을 호흡의 50% 위상에 해당하는 한 개의 삼차원단층촬영 영상에 동일하게 적용하여 삼차원치료계획을 만들었다. 삼차원 및 사차원 치료계획에서 선량계산을 위하여 각각 Ray-tracing과 몬테칼로 알고리즘을 사용하였다. 수립된 4개의 치료계획에서 처방선량의 종양체적 포함률 종양체적의 95%를 포함하는 선량인 D95, 종양의 최대선량, 그리고 척수의 최대선량을 비교하였고 종양의 위치에 대한 연관성도 함께 고찰하였다. 결론: 몬테칼로 알고리즘을 사용한 삼차원 및 사차원 치료계획에서 종양이 폐의 하엽에 위치해 있는 경우에는 사차원치료계획에서 종양 포함률이 평균 4.4% 높았던 반면에 종양이 폐의 중엽이나 상엽에 위치해 있는 경우에는 반대로 평균 4.6% 낮았다 또한 D95도 종양이 폐의 하엽에 위치해 있는 경우에는 사차원치료계획에서 평균 4.8% 높았던 반면에 종양이 폐의 중엽이나 상엽에 위치해 있는 경우에는 반대로 평균 1.7% 낮았다. 척수의 최대선량에 대한 비교에서도 종양과 유사한 경향이 나타났다. 치료계획의 차원과 무관하게 Ray-tracing과 몬테칼로 알고리즘 사이의 선량계산 차이는 평균 30% 정도로 몬테칼로 알고리즘을 사용하였을 때 처방선량이 포함하는 종양의 부피는 크게 줄어들었다. 결론: 폐 종양의 삼차원 및 사차원 치료계획 사이의 차이를 종양과 척수의 선량분포를 통해 비교하였다. 두 치료계획 사이에서 planning target volume (PTV) 포함률이나 D95와 같이 종양과 관련된 선량학적 인자들의 차이 또는 척수의 최대선량 차이는 종양의 이동크기와 형태변화의 정도에 밀접하게 연관되어 있는 것으로 나타났다. 또한, 치료계획의 차원과 무관하게 몬테칼로 알고리즘을 사용하면 처방선량이 포함하는 PTV 포함률이나 D95가 크게 줄어드는 것을 확인하였다.

Purpose: To compare the dose distributions between three-dimensional (3D) and four-dimensional (4D) radiation treatment plans calculated by Ray-tracing or the Monte Carlo algorithm, and to highlight the difference of dose calculation between two algorithms for lung heterogeneity correction in lung cancers. Materials and Methods: Prospectively gated 4D CTs in seven patients were obtained with a Brilliance CT64-Channel scanner along with a respiratory bellows gating device. After 4D treatment planning with the Ray Tracing algorithm in Multiplan 3.5.1, a CyberKnife stereotactic radiotherapy planning system, 3D Ray Tracing, 3D and 4D Monte Carlo dose calculations were performed under the same beam conditions (same number, directions, monitor units of beams). The 3D plan was performed in a primary CT image setting corresponding to middle phase expiration (50%). Relative dose coverage, D95 of gross tumor volume and planning target volume, maximum doses of tumor, and the spinal cord were compared for each plan, taking into consideration the tumor location. Results: According to the Monte Carlo calculations, mean tumor volume coverage of the 4D plans was 4.4% higher than the 3D plans when tumors were located in the lower lobes of the lung, but were 4.6% lower when tumors were located in the upper lobes of the lung. Similarly, the D95 of 4D plans was 4.8% higher than 3D plans when tumors were located in the lower lobes of lung, but was 1.7% lower when tumors were located in the upper lobes of lung. This tendency was also observed at the maximum dose of the spinal cord. Lastly, a 30% reduction in the PTV volume coverage was observed for the Monte Carlo calculation compared with the Ray-tracing calculation. Conclusion: 3D and 4D robotic radiotherapy treatment plans for lung cancers were compared according to a dosimetric viewpoint for a tumor and the spinal cord. The difference of tumor dose distributions between 3D and 4D treatment plans was only significant when large tumor movement and deformation was suspected. Therefore, 4D treatment planning is only necessary for large tumor motion and deformation. However, a Monte Carlo calculation is always necessary, independent of tumor motion in the lung.

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피인용 문헌

  1. Radiation-Induced Pulmonary Injury after Cyberknife Radiosurgery for Lung Malignancy: CT Appearance vol.65, pp.3, 2010, https://doi.org/10.3348/jksr.2011.65.3.257
  2. 소분할 방사선치료 방식에 따른 광중성자 평가 vol.15, pp.12, 2010, https://doi.org/10.5392/jkca.2015.15.12.347